Cork filled plastic bag wad for shot gun shell



Oct. 25, 1966 E. MATTARELLI CORK FILLED PLASTIC BAG WAD FOR SHOT GUN SHELL Filed May 13, 1965 FIG. 3

FIG. 2

FIG. I

FIG. 5

FIG. 4

INVENTOR QNNIO MRTT'A KECL United States Patent 3,280,745 CORK FILLED PLASTIC BAG WAD FOR SHOT GUN SHELL Ennio Mattarelli, Via Procaccini 6, Bologna, Italy Filed May 13, 1965, Ser. No. 455,522 Claims priority, application Italy, May 22, 1964, 11,273/ 64 3 Claims. (Cl. 102-42) The present invention relates generally to a shot gun cartridge and is particularly directed to a packing or wad construction which is disposed between the propellant and the shot of the cartridge.

A primary requisite in shot gun cartridge is that there exist an effective sealing between the shot and propellant so as to prevent the gases of explosion of the propellant from escaping too rapidly so as to exert the maximum impelling forces upon the shot to secure maximum muzzle velocity. Also of importance is that there be means to sufficiently cushion or damp the initial violence of the explosion of the propellant so as to prevent deformation of the shot.

Various packing means or wads have been evolved in the past in order to secure the above-mentioned qualities. Prior art constrictions, although possibly effective in sealing, suffer from excessive friction thereby reducing the forces exerted upon the shot and alternately, if effective in reducing friction, do not seal properly. The present invention overcomes these deficiences and others as will become readily apparent from the following description.

It is therefore a primary object of the present invention to provide a wad having superior sea-ling qualities and minimal frictional characteristics, said wad being constructed of tough, flexible, strong thermoplastic material which possesses sliding surface characteristics.

It is a further object to provide a wad of a configuration and construction such that the initial exposive impact upon the shot is properly damped, as a result of the high shock absorbent characteristics of the material forming the wad.

It is an additional object to provide a wad of a simple, rugged, compact construction which has high tensile strength and toughness and will not readily disintegrate upon explosive impact and which does not require expensive manufacturing techniques.

Other objects and advantages of the present invention will become apparent to those skilled in the art following a reading of the present description, taken in conjunction with the accompanying drawings, forming a part hereof, in which:

FIG. 1 is a front view of the wad;

FIG. 2 is a plan view of the same;

FIG. 3 is a longitudinal sectional view of the same;

FIG. 4 is a longitudinal section view of the wad disposed inside a conventional shot gun cartridge; and

FIG. 5 is a longitudinal sectional view of the wad under dynamic conditions.

Referring now to the drawings and especially to FIG. 4, there is seen a generally conventional shot gun cartridge incorporating the wad of the present invention. The cartridge includes the usual casing 11 of any suitable material such as metal or cardboard, a primer 13, propellant charge 12 and a max of shot 10. The shot is confined at the head end of the cartridge by a disc 14, which in turn is retained in position by a crimped over edge portion 15 of the casing, and rearwardly by the wad of the present invention.

The wad of this invention incorporates a cup 1 of a hollow, generally cylindrical configuration having a forward open end and a convexly shaped rearward end portion 3 and is formed with longitudinally extending grooves 7 on the outer periphery thereof generally uniformly spaced by portions 6. As seen in FIG. 3, for example, the grooves 7 are of a substantial length indicated by numeral 5 and leaving a portion 4 of the cup with smooth outer surface. The particular length of the grooves are dependent on a number of variables as will hereinafter be explained.

Disposed within the cup 1 is a filling or cushion 2 which is preferably of a cork composition but which may be of any other material such as felt, pulp or other fibrous material, or any other material conventionally used for wads. The main criteria for mate-rial selection is that it cushion or dampen the shot and is able to withstand, at least to some degree, the heat and pressures generated by the propellant.

The preferred thermoplastic material of the cup 1 is a polyolefin, such as polyethylene, polypropylene, or ethylene-propylene copolymer, although another synthetic polymer of the thermoplastic type, such as styrene-butadiene copolymer, polyacrylonitrile, vinyl acetateethylene interpolymer and acrylonitriIe butadiene copolymer may be used. Also, cellulose acetate, ethyl cellulose or cyano ethyl cellulose, for example, may be employed.

The effect of the explosion upon the wad will now be described. Upon explosion, the generated gases exert a generally uniform pressure upon the convex portion 3 of the cup as is indicated by the force vectors 8 in FIG. 5. The effect of the explosion causes the convex portion to collapse and to take a generally flat or slightly bowed or concave shape and radial stresses are set up thereby in the rear portion of the cup so as to cause a deformation or buckling of the cup in the vicinity of the peripheral edge 15 between the cylindrical portion 1 and the convex portion 3 resulting in the formation of a peripheral protuberance or bead 9.

The bead formation 9 blocks the passage of propellant gases between the wad and casing so that the full energy of the explosion less the energy absorbed by the cushion 2 is exerted to the shot and continues to provide a seal in passing through the casing into the barrel of the gun.

The portion 3 in being deformed during explosion compresses the cushion 2 and, as a result thereof, the cushion exerts outwardly directed radial forces upon the cylindrical portions 4 and 5 resulting in at least a slight radial expansion thereof. In so doing, the portions 4 and 5 are forced against the inner wall of the casing. Although possibly insignificant, this action aids at least to a minor degree in complementing the sealing function of the head 9, there would result an undesirable amount of friction if the grooves 7 were not provided. The provision of the grooves 7 reduce the surface contact area between the wad and casing and thus reduce the friction of the wad passing through the casing. It is contemplated that the surface of the wad may be coated with a suitable lubricant film, e.g. a film of molybdenum disulfite, graphite or a film of lard oil, or a film of stearic acid di-amide of ethylene diamine. It is apparent that the relative length of grooves would depend upon several variables such as the materials employed for the cup and cushion, type of propellant and the like in order to secure optimum sealing and minimum friction.

It is contemplated that the cup 1 may be provided with extremely small longitudinally extending grooves (not shown) about the outer peripheral surface of portion 4 for the purpose of quickly allowing the air to escape during mechanical assembly operations.

It should be understood that changes in the form, construction and arrangement of the wad of the present invention may be made and substituted for those shown herein and described without departing from the nature and principle of the present invention.

Having thus described the invention, what is claimed and desired to secure by Letters Patent is:

1. In a shot gun cartridgehaving a casing and a propellant, a wad comprising a hollow cup means of one piece plastic having a generally tubular portion, longitudinal grooves in the outer surface of said tubular portion extending longitudinally from one end of said tubular portion part way to the other end to reduce the surface contact area between said wad and the casing, and a convex end portion integrally closing said other end and positioned adjacent said propellant, said convex end portion defining a concave surface on the internal surface of said cup means, a compressible mass of cork composition contained within and completely filling the hollow inner portion of said cup means, said convex portion distorting concavely upon explosion of the propellant to form a radially extending bead portion about the periphery of said tubular portion at the said other end to form a seal between said wad and said casing.

2. In a shot gun cartridge, a wad according to claim l 1, wherein said cup means is molded of polyethylene material.

3. In a shot gun cartridge according to claim 1, a wad wherein the outer surface of the cup means is coated with a lubricant material deposited as a film.

References Cited by the Examiner UNITED STATES PATENTS BENJAMIN A. BORCHELT, Primary Examiner.

' ROBERT F. STAHL, Examiner. 

1. IN A SHOT GUN CARTRIDGE HAVING A CASING AND A PROPELLANT, A WAD COMPRISING A HOLLOW CUP MEANS OF ONE PIECE PLASTIC HAVING A GENERALLY TUBULAR PORTION, LONGITUDINAL GROOVES IN THE OUTER SURFACE OF SAID TUBULAR PORTION EXTENDING LONGITUDINALLY FROM ONE END OF SAID TUBULAR PORTION PART WAY TO THE OTHER END TO REDUCE THE SURFACE CONTACT AREA BETWEEN SAID WAD AND THE CASING, AND A CONVEX END PORTION INTEGRALLY CLOSING SAID OTHER END AND POSITIONED ADJACENT SAID PROPELLANT, SAID CONVEX END PORTION DEFINING A CONCAVE SURFACE ON THE INTERNAL SURFACE OF SAID CUP MEANS, A COMPRESSIBLE MASS OF CORK COMPOSITION CONTAINED WITHIN AND COMPLETELY FILLING THE HOLLOW INNER PORTION OF SAID CUP MEANS, SAID CONVEX PORTION DISTORTING CONCAVELY UPON EXPLOSION OF THE PROPELLANT TO FORM A RADIALLY EXTENDING BEAD PORTION ABOUT THE PERIPHERY OF SAID TUBULAR PORTION AT THE SAID OTHER END TO FORM A SEAL BETWEEN SAID WAD AND SAID CASING. 